This invention relates to electrochromic devices which have an extensive use varied from transmission-type devices such as smart windows, reflective-type devices such as antiglare mirrors for automobiles, reflective-type devices such as decorative mirrors to displays.
A method of forming a chromogenic layer for an electrochromic device is known from Japanese Laid-Open Patent Publication No. 63-18336 disclosing a method in which a film of chromogenic layer is formed by vacuum-epaporation or sputtering an inorganic oxide such as tungsten oxide (WO3) over a transparent electrically conductive film. However, this method requires techniques carried out under vacuum conditions, which lead to elevated production costs.
After an extensive research and study, it has been found that the foregoing disadvantage can be overcome by providing an electrochromic device having a structure described below.
According to one embodiment of the present invention, there is provided an electrochromic device having an ion conductive layer obtained by curing a composition containing (A) a bipyridinium compound represented by formula (1), (B) a metallocene compound represented by formula (2) or (2xe2x80x2) and (C) a precursor of a polymeric solid electrolyte, disposed between two electrically conductive substrates at least one of which is transparent,
formula (1) being 
wherein Xxe2x88x92 and Yxe2x88x92 may be the same or different and are each independently a counter anion selected from the group consisting of an halogen anion, ClO4xe2x88x92, BF4xe2x88x92, PF6xe2x88x92, CH3COOxe2x88x92 and CH3(C6H4)SO3xe2x88x92, R1 is hydrogen or a C1-C5 alkyl group, R2 is a C1-C30 divalent hydrocarbon residue, R3 is a C1-C20 hydrocarbon residue and a is an integer of 0 or 1; formulae (2) and (2xe2x80x2) being 
wherein R4 and R5 are each independently a hydrocarbon group selected from the group consisting of C1-C10 alkyl, alkenyl and aryl groups, if R4 or R5 is an aryl group, the aromatic ring may form a condensation ring by bonding to a cyclopentadienyl ring, n1 is an integer of 0xe2x89xa6n1xe2x89xa64, n2 is an integer of 0xe2x89xa6n2xe2x89xa65, A and Axe2x80x2 may be the same or different and are each independently a monovalent group, m is 0 or 1, M is selected from the group consisting of Cr, Co, Fe, Mg, Ni, Os, Ru and V, Mxe2x80x2 is selected from the group consisting of Hf, Mo, Nb, Ti, V and Zr and Q and Qxe2x80x2 may be the same or different and each are independently hydrogen, halogen and a C1-C12 alkyl group;
formula (A) being 
wherein R6 is hydrogen or methyl group, R7 is hydrogen or methyl group, b is 0 or 1 and provided that R7 is hydrogen if b is 0.
According to the other embodiment of the present invention, there is provided an electrochromic device having an ion conductive layer obtained by curing the composition further containing (D) an ultraviolet absorbing compound having an ethylenic double bond.